The present invention relates to a system for controlling the proportion of leaf vein in a tobacco raw material treating process.
Generally, in a tobacco manufacturing process, a raw leaf tobacco is first unfastened leaf by leaf, then softened with water and steam by means of a humidity controller, thereafter peeled off into a mesophyll portion (hereinafter referred to as "lamina") and a leaf vein portion (hereinafter referred to as "vein") by vein removing means and separated into lamina and vein by separator means. The lamina is dried to a moisture content of 12% so as to not to cause deterioration or the growth of mold during a long term storage and packed into a cask or other container (the process described so far is a raw material treating process), then stored for aging over a long period. After aging, the lamina is shredded into shred tobacco.
Thus, in the raw material treating process the leaf tobacco is peeled off into lamina and vein by vein removing means and then separated into lamina and vein by separator means. In this case, the degree of the separation greatly affects the yield and quality of product. More particularly, if the separation is performed so as not to incorporate vein in lamina, the quality of product will be improved, but a considerable quantity of lamina will remain on the vein side at the time of separation, thus leading to a very poor yield. On the other hand, if the vein is allowed to remain in the lamina at the time of separation, the yield will be improved, but the quality of product is severely deteriorated. Therefore, it is necessary to suitably control the proportion of vein contained in lamina (hereinafter referred to as the "proportion of vein or vein proportion") in consideration of the quality of product and yield to minimize the loss of lamina.
Heretofore, the proportion of vein has been controlled to an optimum value by human power. More particularly, the damper opening of winnowing means is changed according to a table of predetermined operation conditions to set a winnowing air velocity, then the operator manually holds the lamina discharged by separation, judges the proportion of vein according to the sense of touch, and when the proportion of vein is larger than a predetermined value, the damper opening is made smaller to decrease the air velocity, while when the vein proportion is smaller than the predetermined value, the damper opening is made larger to increase the air velocity.
However, if properties (area, weight, density, etc.) of the raw material which influence the separation efficiency (ratio of the lamina separated by winnowing means to the lamina fed into the winnowing means) change, the proportion of vein also changes, so it is very troublesome to determine operating conditions in advance according to the kind of raw material as in the prior art. Besides, a considerable skill is required for judging the proportion of vein according to the sense of touch, and this judgment is not so exact because of individual variations.
For the above reasons, it has heretofore been difficult to make quality control by controlling the proportion of vein.